Quiero comes from the word querer, which means like, but when people say it, they mean "I love you". Te quiero is more of a friendly "I love you" it is mostly used by friends and family. It also can be used to express the first feeling you feel when you start a relationship with someone. Te amo is more passionate. It's more appropriate to use it towards somebody you strongly love/are in love with. Feelings that come from deep within your heart of wanting to make that person happy and sharing your life with him. Te adoro means to adore, Feeling admiration for the other person...Ex: You admire the way he is or the way he treats others. Hope I helped :)

In Spain,"te quiero" is the only expression we use nowadays with the implications that "I love you" has in English. "Te amo" would sound terribly affected, even in a love letter, although you will find it in literary sources, especially those written before the 1960-70s. As to "Te adoro", it literally expresses "I worship you" and therefore would sound hyperbolic, or even comic, in most circumstances if interpreted literally, but it is not so interpreted, in general. In certain cases, it is ironic: After many years of marriage She says: "¿Me quieres?" And He replies: "Te adoro" ;-). A relevant difference with respect to "Te quiero", anyway, is that "Te adoro" has no (or very slight) sexual connotations; it rather expresses sublimated love. In Spanish, 'adorar' is more common in expressions like 'adora al niño/a su hermano/a su abuela,'... etc. In general, if somebody "te adora", they admire you, care for you, would do anything for you, etc., but they may very well not like you or want you as a sexual partner. [All this is probably not exactly so in Latin America, though; do not interpret it as applicable to all varieties of Spanish].

In my personal point of view, "te adoro" (meaning "I adore you") has a stronger feeling to worship someone, for instance, the fans worship their idols; while "te amo" (meaning "I love you") and "te quiero" (literally meaning "I want you") are in general an expression of a love feeling. In Spanish, however, people tend to use "te quiero" more frequently to express "I love you", especially in conversations. Hence, I would say that Spanish provides an alternative way of such expression; while in Italian or in Portuguese, the term is solely expressed as "ti amo" or "te amo", respectively. [Native speakers, please kindly rectify the above presumptions should they be incorrect.] Take care and good day. / Cuídate, y que tengas buenos días.

hi is the feeling of love, but when you say worship is much more intense